1. Field of the Invention
The invention relates to environmental pollution control. More particularly, the invention relates to a method for removing and recovering volatile contaminants from wastewater. Most particularly, the invention relates to the use of activate carbon to adsorb aromatic hydrocarbons.
2. Description of other Relevant Methods in the Field
A variety of technologies have been developed and utilized to remove volatile contaminants such as hydrocarbons from chemical plant and refinery wastewater in order to render it safe for discharge into the surface and ground water supply. These technologies have been driven by the discovery that water sources proximate to industrial areas have become contaminated with volatile organic compounds such as benzene, toluene, chlorinated and halogenated solvents and other compounds derived from petroleum.
A common method used in the petroleum industry for removing volatile organic compounds has been to air strip the wastewater in a packed tower. The wastewater is stripped in a vertically oriented tower at atmosphere pressure. Contaminated wastewater is pumped into the upper portion of the packed tower and cascades downwardly through liquid-gas contacting media referred to in the art as packing. In the alternative, a series of contacting trays may be substituted for the packing. Air is forced upwardly through the packing by means of a blower or fan to volatilize organic compounds. The contaminant free wastewater is collected at the bottom of the tower and is removed for disposal consistent with any remaining contamination. The contaminant laden air is released from the top of the tower to the atmosphere. In the alternative, the air is collected and purified to reduce hydrocarbon content before release to the atmosphere.
A number of methods have been developed for separating hydrocarbon for pollution control. U.S. Pat. No. 4,054,429 to N. Ostojic et al. teaches a method and apparatus for recovering solvent from a gas such as air. By the method, solvent contaminated air is passed through an oil absorber which absorbs the solvent, producing a clean air product. The oil-solvent mixture is stripped with inert gas to produce a solvent free oil. The remaining inert gas-oil mixture is separated by first condensing the oil and then passing the inert gas through an activated charcoal filter which removes last traces of solvent from the inert gas. Cleaned inert gas is returned to the stripper for recycle in the oil-solvent stripping stage.
U.S. Pat. No. 3,876,505 to G. R. Stoneburner discloses a method of making granular activated carbon from bituminous coal. The activated carbon is made by sizing, drying, oxidizing and activating.
U.S. Pat. No. 4,014,817 to B.C. Johnson et al. discloses a method of making granular activated carbon from bituminous coal. The coal is acid washed before manufacture to slow down the activation procedure.